One application for power-driven booms is in the repair of large smelting drums in converters for smelting metal ore. Drums of this type consist of cylindrical chambers having horizontal longitudinal axes and openings in their annular walls for access to the chambers. During the smelting process, deposits of hardened material build up near the openings to the drums as well as on various inner surfaces within the drums. These deposits are removed by hydraulic reciprocating hammers which chisel the deposits away from the inner walls of the drums.
A hammer of this type is supported at the distal end of a jointed boom which is inserted into the drum through the opening. In a preferred construction, the jointed boom consists of an elongated boom member hinged at a proximal end to a base and a stick member hinged near its proximal end to a distal end of the boom member. The boom member, stick member and hammer are each coupled near their proximal ends to hydraulic cylinders which cooperate to position the hydraulic hammer near the deposits in the drum.
It is desirable that the stick member be made as light as possible to minimize the power required to position the hammer. At the same time, it is desirable that the stick be made as rugged as possible to withstand the periodic forces generated as the hammer strikes a surface to be cleaned. These reaction forces propagate through the rotating stick in the form of elastic waves. For example, the magnitude of these reaction forces may be as high as 10,000 foot-pounds.